Conventional stripping and cleaning formulations for Al back-end-of the-line (Al BEOL) cleaning of ashed and unashed substrates typically contain a hydroxlyamine, a solvent (optional), an alkanolamine (optional), water and a corrosion inhibitor or chelating agent. Conventional chemistries typically contain a majority of organic components and amines and a minority of water. Typical examples of such chemistries are seen in U.S. Pat. No. 5,911,835, U.S. Pat. No. 6,110,881, U.S. Pat. No. 6,319,885, U.S. Pat. No. 7,051,742, and U.S. Pat. No. 7,144,849. In the above listed patents, dihydroxy-aromatic corrosion inhibitors, of which catechol (dihydroxybenzene) is commonly used. Catechol has been used as a corrosion inhibitor for aluminum. In addition, catechol has been used as a chelating agent to extend the stability of hydroxylamine-containing formulation.
It is well known to those in the art that a key property of an effective cleaner is its ability to attack and/or dissolve post-etch and/or post-ash residues without substantially attacking the underlying interconnect dielectric or metals, that is, the selection of corrosion inhibitor is the key to controlling the metal etch rate.
In BEOL applications for Al interconnect structures, the corrosion inhibitor must be able to inhibit etching of aluminum and other interconnect metals/film, however since aluminum is electrochemically very active, it is most susceptible to corrosion and/or etching.
It would therefore be desirable to provide a cleaning formulation and process capable of removing those unwanted residues without corroding, dissolving or dulling the exposed surfaces of the interconnect structures. Hydroxylamine is very effective at removing residues and unashed photoresist from semiconductor substrates, but is susceptible to decomposition, even at room temperature. It is critical to find components for the cleaning formulation containing hydroxylamine that can stabilize hydroxylamine or do not accelerate hydroxylamine decomposition. Therefore, it would be desirable to control aluminum etch rate and to stabilize hydroxylamine for the cleaning formulation containing hydroxylamine.